Abstract

Oxidative stress plays an important role in aging-related neurodegeneration. This study used littermates of WT and Nox2-knockout (Nox2KO) mice plus endothelial cell–specific human Nox2 overexpression–transgenic (HuNox2Tg) mice to investigate Nox2-derived ROS in brain aging. Compared with young WT mice (3–4 months), aging WT mice (20–22 months) had obvious metabolic disorders and loss of locomotor activity. Aging WT brains had high levels of angiotensin II (Ang II) and ROS production; activation of ERK1/2, p53, and γH2AX; and losses of capillaries and neurons. However, these abnormalities were markedly reduced in aging Nox2KO brains. HuNox2Tg brains at middle age (11–12 months) already had high levels of ROS production and activation of stress signaling pathways similar to those found in aging WT brains. The mechanism of Ang II–induced endothelial Nox2 activation in capillary damage was examined using primary brain microvascular endothelial cells. The clinical significance of Nox2-derived ROS in aging-related loss of cerebral capillaries and neurons was investigated using postmortem midbrain tissues of young (25–38 years) and elderly (61–85 years) adults. In conclusion, Nox2 activation is an important mechanism in aging-related cerebral capillary rarefaction and reduced brain function, with the possibility of a key role for endothelial cells.

Figure 7

(A) BMEC O2•– production detected by lucigenin chemiluminescence in the presence of SCP or Nox2tat. (B) Lipid peroxidation in BMEC homogenates as detected by MDA assay. (C) Nox2 expression and activation of stress signaling pathways as detected by Western blot analysis. ODs of protein bands were quantified and normalized to α-tubulin detected in the same samples. The phospho-ERK1/2 and γH2AX bands were normalized to the total protein bands detected in the same samples, expressed as OD P/T. (D) Cell senescence and capillary damage. Top row: BMEC senescence as detected by SAβG activity assay (blue). Scale bar: 100 μm. Bottom row: Ang II–induced capillary damage on Matrigels. Scale bar: 500 μm. *P < 0.05 for indicated values versus control values in the same treatment group; †P < 0.05 for indicated values versus Ang II SCP values. n = 4 separate BMEC isolations/group. Three mice were used for each BMEC isolation. Statistical analysis was performed using 1-way ANOVA followed by Bonferroni’s post hoc tests.